Thermoplastic resin composition, resin molded article, and plated article

Abstract

An object of the present invention is to provide a thermoplastic resin composition which is excellent in impact resistance and fluidity during molding processing, is also excellent in plating adhesion strength, plating appearance, and thermal cycle characteristics, and is capable of maintaining plating adhesion even in a thermal shock test, and a resin molded article and a plated product (decorative part) using the same.SOLUTION: A thermoplastic resin composition is a melt-kneaded product of a rubber-containing graft copolymer (A) obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the presence of a rubbery polymer, and a copolymer (B) obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, the copolymer (B) being independent of the rubber-containing graft copolymer (A), in which a calcium content with respect to a total mass of the thermoplastic resin composition is 0.3% by mass or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composition, a resin molded article, and a plated article. This application claims priority to Japanese Patent Application No. 2024-003220, filed on January 12, 2024, the contents of which are incorporated herein by reference. [Background technology]

[0002] Due to their excellent impact resistance, mechanical strength, and chemical resistance, molded products made from ABS resin are used in a wide range of fields, including office equipment, information and communication equipment, electronic and electrical equipment, home appliances, automobiles, and construction. Furthermore, when plated, molded products made from ABS resin have excellent plating appearance, high plating film adhesion strength, and excellent thermal cycle properties, making them suitable for a wide variety of plastic plating applications. For example, in the automotive industry, ABS resin is being used in plating applications such as radiator grille parts and emblem parts.

[0003] Plating characteristics are easily affected by factors such as the properties of the resin composition used to form the molded product and molding conditions. Therefore, even when a resin composition containing ABS resin is used, poor plating appearance can occur. If molding conditions are poor, poor appearance phenomena such as peeling or lifting of the plating film can occur, significantly reducing the commercial value of the final product. Therefore, a thermoplastic resin composition containing a graft copolymer with a different rubber particle size and a specific copolymer other than the graft copolymer in a specified ratio has been proposed as a thermoplastic resin composition that provides a plating film with high adhesion strength and does not cause swelling or cracks in the plating film even during thermal cycles (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent No. 6218347 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the thermoplastic resin composition of Patent Document 1 is plated, plating adhesion is achieved and a certain degree of effectiveness is demonstrated in a thermal cycle test (also called a "heat cycle test" or "cooling cycle test," which involves repeated, gradual temperature changes over time). However, in a thermal shock test (which involves repeated, rapid temperature changes over time), the plating film is prone to swelling and peeling, which can impair the decorative properties of the product or impair its functionality as a part.

[0006] The present invention aims to provide a thermoplastic resin composition that has excellent impact resistance and fluidity during molding, and is also excellent in plating adhesion strength, plating appearance, and thermal cycle characteristics, and that can maintain plating adhesion even in a thermal shock test, as well as a resin molded product and a plated product (decorated part) that use the same. [Means for solving the problem]

[0007] The present invention includes the following aspects. [1] A rubber-containing graft copolymer (A) obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the presence of a rubber polymer; A thermoplastic resin composition which is a melt-kneaded product of the rubber-containing graft copolymer (A) and a copolymer (B) which is independent of the rubber-containing graft copolymer (A) and is obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, the rubber-containing graft copolymer (A) is mixed with 20 to 60 parts by mass of the copolymer (B) and the rubber-containing graft copolymer (A) with 40 to 80 parts by mass of the copolymer (B) relative to 100 parts by mass in total of the rubber-containing graft copolymer (A) and the copolymer (B); when the molecular weights of all polymers in the copolymer (B) are measured by a GPC method in terms of standard polystyrene, the proportion of polymers having a molecular weight of less than 50,000 is 20 mass% or less based on the total mass of all polymers; the total content of the rubber-containing graft copolymer (A) and the copolymer (B) is 75 to 100% by mass based on the total mass of the thermoplastic resin composition; A thermoplastic resin composition, wherein the calcium content in the thermoplastic resin composition is 0.30 mass % or less relative to the total mass of the thermoplastic resin composition. [2] The thermoplastic resin composition according to [1], wherein, among all polymers of the copolymer (B), the proportion of polymers in which the proportion of repeating units derived from a vinyl cyanide compound is 10 to 30 mass% of all repeating units is 85 to 100 mass% relative to the total mass of all polymers. [3] The thermoplastic resin composition according to [1] or [2], wherein the copolymer (B) is a mixture of a plurality of copolymers (B), and when the mass average molecular weight of each copolymer (B) is measured in terms of standard polystyrene by a GPC method, the mixing ratio of copolymers (B) having a mass average molecular weight of 50,000 to 300,000 relative to the total mass of the mixture is 85 to 100 mass%. [4] The thermoplastic resin composition according to any one of [1] to [3], wherein the copolymer (B) is a mixture of copolymer (BI) and copolymer (BII), wherein the copolymer (BI) is a copolymer obtained by polymerization of a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, wherein the content of the vinyl cyanide compound relative to the total mass of the monomer mixture is 10 to 30 mass%, and the mass average molecular weight of the copolymer (BI) is 50,000 to 150,000 as measured by a GPC method in terms of standard polystyrene; and the copolymer (BII) is a copolymer obtained by polymerization of a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, wherein the content of the vinyl cyanide compound relative to the total mass of the monomer mixture is 10 to 30 mass%, and the mass average molecular weight of the copolymer (BII) is greater than 150,000 and up to 300,000 as measured by a GPC method in terms of standard polystyrene. [5] The thermoplastic resin composition according to any one of [1] to [4], wherein the calcium content in the thermoplastic resin composition is 0.20 mass% or less relative to the total mass of the thermoplastic resin composition. [6] A resin molded article made of the thermoplastic resin composition according to any one of [1] to [5]. [7] A plated product having a plating film on at least a part of the surface of the resin molded product according to [6]. [Effects of the Invention]

[0008] The present invention provides a thermoplastic resin composition that has excellent impact resistance and flowability during molding, excellent plating adhesion strength, plating appearance, and thermal cycle characteristics, and that can maintain plating adhesion even in a thermal shock test. Furthermore, it is possible to provide a resin molded product and a plated product (decorated part) using the same. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following definitions of terms apply throughout the specification and claims. The "molded resin article" is an article obtained by molding the thermoplastic resin composition of the present invention. The term "plated product" refers to a resin molded product that has been subjected to a plating treatment, and has a plating film on at least a portion of the surface of the resin molded product. "Thermal cycle characteristics" refers to the property of the plating film of a plated product undergoing minimal change in temperature during a test in which gradual temperature changes are repeated periodically over time. "Thermal shock characteristics" refers to the property of the plating film of a plated product undergoing minimal change in a test in which rapid temperature changes are repeated periodically over time. "(Meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. "(Meth)acrylate" is a general term for acrylate and methacrylate. The symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0010] Hereinafter, the rubber-containing graft copolymer (A), copolymer (B), and other components, which are the materials of the thermoplastic resin composition of the present invention, will be explained, and then the thermoplastic resin composition of the present invention will be explained.

[0011] <Rubber-containing graft copolymer (A)> The rubber-containing graft copolymer (A) is a copolymer in which a monomer component (a) is graft-polymerized onto a rubbery polymer. In the case of rubber-containing graft copolymer (A), it is not easy to identify how the monomer component (a) is polymerized onto the rubber polymer. In other words, there are circumstances (impossible or impractical circumstances) that make it impossible or impractical to directly identify the graft copolymer (A) based on its structure or properties. Therefore, it is more appropriate to define graft copolymer (A) as "a rubber polymer to which the monomer component is graft polymerized."

[0012] (rubber polymer) Examples of rubbery polymers constituting the rubber-containing graft copolymer (A) include butadiene-based rubbers such as polybutadiene, styrene-butadiene copolymer, and acrylate-butadiene copolymer; conjugated diene-based rubbers such as styrene-isoprene copolymer; acrylic rubbers such as polybutyl acrylate; olefin-based rubbers such as ethylene-propylene copolymer; and silicone-based rubbers such as polyorganosiloxane. These rubbery polymers can be used in the form of a monomer. The rubbery polymer may have a composite rubber structure or a core / shell structure. As the rubbery polymer, butadiene rubber is preferred in view of the good balance of plating characteristics (plating adhesion strength and plating appearance) and color tone and impact resistance. These rubbery polymers may be used alone or in combination of two or more.

[0013] The volume average particle diameter of the rubbery polymer is preferably 200 to 500 nm, more preferably 250 to 440 nm, and even more preferably 280 to 380 nm. When the volume average particle diameter of the rubbery polymer is equal to or greater than the lower limit, the thermal shock properties of the plated product are further improved. When the average particle diameter of the rubbery polymer is equal to or less than the upper limit, the plating adhesion strength of the plated product is further increased. In addition, the flowability of the thermoplastic resin composition is improved.

[0014] The method for producing the rubber polymer is not particularly limited, but emulsion polymerization is preferred because it is easy to control the particle size. Known methods can be used for emulsion polymerization, and there are no particular limitations on the catalysts, emulsifiers, etc. that can be used, and various types can be used.

[0015] The rubber polymer may be an enlarged rubber. The average particle size, distribution, etc. can be adjusted by the enlargement procedure. Examples of the enlargement method include mechanical coagulation, chemical coagulation, and coagulation using an acid group-containing copolymer. Chemical coagulation methods include adding an acidic substance to a rubber polymer latex to destabilize emulsion stability and cause coagulation. Once the target particle size is reached, an alkaline substance is added to re-stabilize the rubber polymer latex. Examples of acidic substances include acetic acid, acetic anhydride, sulfuric acid, and phosphoric acid. Examples of alkaline substances include potassium hydroxide and sodium hydroxide. An example of a coagulation method using an acid group-containing copolymer is a method of obtaining an enlarged rubber latex by mixing a rubber polymer latex with an acid group-containing copolymer latex. Examples of the acid group-containing copolymer latex include an acid group-containing copolymer latex obtained by polymerizing, in water, a monomer component containing an acid group-containing monomer (e.g., a carboxy group-containing monomer such as (meth)acrylic acid), an alkyl (meth)acrylate monomer, and, if necessary, other monomers copolymerizable therewith.

[0016] The volume average particle size of the rubber polymer can be measured using a measuring instrument such as that used in the examples described later. The volume average particle size of the rubbery polymer can be controlled by adjusting the polymerization conditions (temperature, time, etc.) during the production of the rubbery polymer, and the types and blending ratios of the monomers. Such rubber polymers are commercially available as rubber latexes. Latexes of rubber polymers having different volume average particle diameters can also be mixed, and in this case, the volume average particle diameter can be adjusted to fall within a preferred range.

[0017] (Monomer component (a)) The monomer component (a) constituting the rubber-containing graft copolymer (A) contains an aromatic vinyl compound (a1), a vinyl cyanide compound (a2), and, if necessary, another vinyl compound (a3). Examples of the aromatic vinyl compound (a1) include styrene, α-methylstyrene, vinyltoluenes (e.g., p-methylstyrene, etc.), halogenated styrenes (e.g., p-bromostyrene, p-chlorostyrene, etc.), p-tert-butylstyrene, dimethylstyrene, vinylnaphthalene, etc. Among these, styrene and α-methylstyrene, etc. are preferred. These aromatic vinyl compounds (a1) may be used alone or in combination of two or more.

[0018] Examples of the vinyl cyanide compound (a2) include acrylonitrile and methacrylonitrile, among which acrylonitrile is preferred. These vinyl cyanide compounds (a2) may be used alone or in combination of two or more.

[0019] The other vinyl compound (a3) ​​may be a vinyl compound copolymerizable with the aromatic vinyl compound (a1) and the vinyl cyanide compound (a2). Examples of such vinyl compounds include alkyl methacrylates such as methyl methacrylate and ethyl methacrylate; alkyl acrylates such as methyl acrylate, ethyl acrylate, and butyl acrylate; maleimide compounds such as N-phenylmaleimide and N-cyclohexylmaleimide; and unsaturated carboxylic acid compounds such as (meth)acrylic acid, itaconic acid, and fumaric acid. These other vinyl compounds (a3) ​​may be used singly or in combination of two or more.

[0020] The proportion of each vinyl compound in the monomer component (a) is preferably such that the aromatic vinyl compound (a1) accounts for 60 to 80 mass %, the vinyl cyanide compound (a2) accounts for 20 to 40 mass %, and the other vinyl compound (a3) ​​accounts for 0 to 20 mass %, relative to the total mass of the monomer component (a). However, the sum of the contents of the aromatic vinyl compound (a1), the vinyl cyanide compound (a2) and the other vinyl compound (a3) ​​does not exceed 100% by mass based on the total mass of the monomer component (a). When the proportion of each compound is within the above range, the moldability of the thermoplastic resin composition, the plating adhesion strength of plated products, the thermal cycle characteristics, the thermal shock characteristics, and the impact strength are improved in balance.

[0021] (Rubber content in rubber-containing graft copolymer (A)) The content of the rubber polymer component in the rubber-containing graft copolymer (A) is preferably 30 to 70 mass %, more preferably 40 to 60 mass %, based on the total mass of the rubber-containing graft copolymer (A). Therefore, the content of the monomer component (a) constituting the rubber-containing graft copolymer (A) is preferably 30 to 70 mass %, more preferably 40 to 60 mass %, based on the total mass of the rubber-containing graft copolymer (A), while keeping the proportion of each vinyl compound in the monomer component (a) within the above-mentioned range. However, the sum of the contents of the rubbery polymer component and the monomer component (a) does not exceed 100% by mass based on the total mass of the rubber-containing graft copolymer (A). When the content of the rubber polymer-derived component in the rubber-containing graft copolymer (A) is within this range, the adhesion strength characteristics, thermal cycle characteristics, thermal shock characteristics, impact resistance, or flowability in the plating process are superior.

[0022] The rubber-containing graft copolymer (A) can be obtained by copolymerizing a monomer mixture (a) containing an aromatic vinyl compound and a vinyl cyanide compound in the presence of a rubbery polymer. The polymerization method is not particularly limited, but emulsion polymerization is preferred because it allows for control so that the reaction proceeds stably. Specific examples include a method in which the monomer mixture is charged all at once to a rubber polymer latex and then polymerized; a method in which a portion of the monomer mixture is first charged to a rubber polymer latex and polymerized as needed while the remainder is added dropwise to the polymerization system; and a method in which the entire amount of the monomer mixture is added dropwise to a rubber polymer latex and polymerized as needed. These methods can be carried out in one or more stages. When carried out in two or more stages, it is also possible to vary the type and composition ratio of the monomers constituting the monomer mixture in each stage. The rubber-containing graft copolymer (A) obtained by emulsion polymerization is usually in the form of a latex.

[0023] In emulsion polymerization, a radical polymerization initiator and an emulsifier are usually used. Examples of the radical polymerization initiator include peroxides, azo initiators, and redox initiators that combine an oxidizing agent and a reducing agent. Among these, redox initiators are preferred, and sulfoxylate initiators that combine ferrous sulfate, ethylenediaminetetraacetic acid disodium salt, sodium formaldehyde sulfoxylate, and hydroperoxide are particularly preferred. The emulsifier is not particularly limited, but carboxylic acid salts such as sodium sarcosinate, potassium fatty acid, sodium fatty acid, dipotassium alkenyl succinate, or rosin acid soap are preferred because they provide excellent latex stability during radical polymerization and can increase the polymerization rate. Among these, dipotassium alkenyl succinate is preferred because it can suppress gas generation when the resulting rubber-containing graft copolymer and a thermoplastic resin composition containing the same are molded at high temperatures. Specific examples of dipotassium alkenyl succinate include dipotassium octadecenyl succinate, dipotassium heptadecenyl succinate, and dipotassium hexadecenyl succinate. These emulsifiers may be used alone or in combination of two or more.

[0024] During the polymerization, various known chain transfer agents may be added to control the molecular weight and graft ratio of the resulting rubber-containing graft copolymer (A). The polymerization conditions may be, for example, 30 to 95°C and 1 to 10 hours. The rubber-containing graft copolymer (A) is usually obtained in the form of a latex. Methods for recovering the rubber-containing graft copolymer (A) from its latex include, for example, a wet method in which the latex of the rubber-containing graft copolymer (A) is coagulated into a slurry by being poured into hot water containing a coagulant dissolved therein, and a spray-dry method in which the rubber-containing graft copolymer (A) is semi-directly recovered by spraying the latex of the rubber-containing graft copolymer (A) into a heated atmosphere. Coagulants used in the wet method include inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid; and metal salts such as calcium chloride, calcium acetate, and aluminum sulfate, and are selected depending on the emulsifier used in the polymerization. For example, when only a carboxylic acid soap such as a fatty acid soap or a rosin acid soap is used as the emulsifier, one or more of the above-mentioned coagulants can be used. When an emulsifier that exhibits stable emulsifying power even in the acidic range, such as sodium alkylbenzenesulfonate, is used as the emulsifier, a metal salt is preferred as the coagulant. When the wet method is used, a rubber-containing graft copolymer (A) in a slurry state is obtained. Methods for obtaining a dry rubber-containing graft copolymer (A) from this slurry rubber-containing graft copolymer (A) include first dissolving the remaining emulsifier residue in water and washing, then dehydrating the slurry using a centrifuge or a press dehydrator, and then drying using a flash dryer, etc.; or simultaneously dehydrating and drying using a squeeze dehydrator or extruder, etc. By these methods, a dry rubber-containing graft copolymer (A) in a powder or particulate state is obtained. The washing conditions are not particularly limited, but washing is preferably carried out under conditions such that the amount of emulsifier residue contained in 100% by mass of the rubber-containing graft copolymer (A) after drying is 2% by mass or less.

[0025] (grafting rate) The graft ratio is the mass (Wa) of the vinyl monomer mixture graft-polymerized onto the rubber polymer, expressed as a percentage ((Wa / Wd) x 100) of the mass (Wd) of the rubber polymer. Generally, the graft ratio can be calculated from the acetone-insoluble portion of the rubber-containing graft copolymer (A) obtained after graft polymerization as follows: Acetone is added to the rubber-containing graft copolymer (A) and the mixture is shaken at 25°C for 2 hours to extract the acetone-soluble matter. The acetone-insoluble matter is then filtered, dried, and its mass is measured, and the graft ratio is calculated using the following formula (1). In the formula (1), "m" is the mass (g) of the rubber-containing graft copolymer (A) before extraction, "n" is the mass (g) of the acetone-insoluble matter, and "L" is the rubber content of the rubber-containing graft copolymer (A), i.e., the mass (% by mass) of the rubbery polymer. The rubber content of the rubber-containing graft copolymer (A) can be calculated from the polymerization recipe and polymerization addition rate, or from infrared absorption spectroscopy. Grafting rate (%) = {(nm × L) / (m × L)} × 100 (1)

[0026] The graft ratio of the rubber-containing graft copolymer (A) is not particularly limited, but is preferably 30 to 120% by mass, more preferably 35 to 100% by mass, even more preferably 40 to 80% by mass, particularly preferably 50 to 80% by mass, and most preferably 60 to 80% by mass. If the graft ratio of the rubber-containing graft copolymer (A) is within the above range, the impact resistance of the resin molded product is further improved, and from the viewpoint of plating processing, adhesion strength is easily exhibited.

[0027] (Mass Average Molecular Weight and Molecular Weight Distribution of Acetone-Soluble Fraction of Rubber-Containing Graft Copolymer (A)) The acetone soluble component of the rubber-containing graft copolymer (A) is a non-grafted copolymer in the rubber-containing graft copolymer (A), and its composition falls within the range of the blending ratio of the monomer component (a). The mass average molecular weight (Mw) of the acetone-soluble portion of the rubber-containing graft copolymer (A) is preferably 50,000 to 500,000, more preferably 60,000 to 300,000, and even more preferably 80,000 to 150,000. The molecular weight distribution (Mw / Mn) is preferably 2.0 to 5.0, more preferably 2.3 to 4.0, and even more preferably 2.6 to 3.5. Having the mass average molecular weight (Mw) and molecular weight distribution (Mw / Mn) within the above ranges provides the thermoplastic resin composition with excellent fluidity and impact resistance, and also improves the balance of plating adhesion strength, thermal cycle properties, and thermal shock properties of plated products. Here, the mass average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the ungrafted copolymer (acetone soluble portion) can be measured as polystyrene equivalent values ​​by GPC, as described in detail in the Examples section below. The content of acetone soluble components in the rubber-containing graft copolymer (A) having a molecular weight of less than 50,000 is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the acetone soluble components.

[0028] The rubber-containing graft copolymer (A) may be a single type or a mixture of multiple types, such as those having different volume average particle sizes of rubber polymers, different monomer composition ratios or mass average molecular weights of acetone soluble components, or those produced by different methods.

[0029] <Copolymer (B)> The copolymer (B) is a copolymer obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the absence of a rubbery polymer. When the molecular weights of all polymers in the copolymer (B) melt-kneaded as a material for the thermoplastic resin composition of the present invention are measured by GPC in terms of standard polystyrene, the proportion of polymers having a molecular weight of less than 50,000 is 20% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 6.5% by mass or less, based on the total mass of all polymers. The lower limit of this proportion may be 0% by mass. By keeping the thickness within this range, the impact resistance and thermal shock characteristics are improved.

[0030] The proportion of copolymer (B) having a molecular weight of less than 50,000 is measured using gel permeation chromatography (GPC). From the measurement results (an elution chart with the elution amount on the vertical axis and the retention time or elution volume on the horizontal axis) of the entire copolymer (B) as a sample, an elution peak showing the molecular weight distribution of the eluted polymer is plotted. The proportion of polymers with a molecular weight of less than 50,000 among all polymers in the sample can be calculated from the proportion of the area of ​​the elution peak occupied by the molecular weight. Here, this molecular weight corresponds to the mass molecular weight. Note that this value is converted from standard polystyrene of known molecular weight.

[0031] Of all the polymers in the copolymer (B) melt-kneaded as a material for the thermoplastic resin composition of the present invention, the proportion of polymers having repeating units derived from vinyl cyanide compounds in a proportion of 10 to 30% by mass (100% by mass of all repeating units) is preferably 85 to 100% by mass relative to the total mass of all the polymers. By keeping the proportion within this range, impact resistance, thermal shock properties, etc., are improved. Here, the proportion of repeating units derived from vinyl cyanide compounds to all repeating units is preferably 10 to 30 mass %, more preferably 15 to 29 mass %, and even more preferably 20 to 28 mass %. The proportion of repeating units derived from a vinyl cyanide compound to all repeating units reflects the content of the vinyl cyanide compound relative to the total mass of the monomer mixture during copolymerization, and is equivalent to that content.

[0032] The copolymer (B) may further contain repeating units derived from other copolymerizable compounds other than the aromatic vinyl compound and the vinyl cyanide compound, as required. Preferred examples of the aromatic vinyl compound, the vinyl cyanide compound, and the other copolymerizable compound used as required as monomers of the copolymer (B) include the compounds (a1), (a2), and (a3) ​​listed above for the rubber-containing graft copolymer (A), respectively.

[0033] The copolymer (B) to be melt-kneaded as a material for the thermoplastic resin composition of the present invention is a material independent of the rubber-containing graft copolymer (A), and may be a single type polymerized independently or a mixture of multiple types polymerized individually.

[0034] [Mixture of copolymers (B)] When the copolymer (B) melt-kneaded as a material for the thermoplastic resin composition of the present invention is a mixture of multiple copolymers (B), the mass-average molecular weight of each copolymer (B) before mixing can be measured individually by GPC in terms of standard polystyrene. After this measurement, the blending ratio Z of copolymers (B) having a mass-average molecular weight of 50,000 to 300,000 relative to the total mass of the mixture is preferably 85 to 100 mass%. This range can further improve the impact resistance or thermal shock properties of the present invention. For example, in a mixture of 10 parts by mass of copolymer (B) having a mass-average molecular weight of 40,000 and 40 parts by mass of copolymer (B) having a mass-average molecular weight of 100,000, the mixing ratio Z is calculated to be 80% by mass (40 parts by mass / 50 parts by mass x 100%).

[0035] The mixture of copolymers (B) is preferably a mixture of specific copolymers (BI) and (BII).

[0036] The copolymer (BI) is a copolymer obtained by polymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound. The content of the vinyl cyanide compound (i.e., the repeating units derived from the vinyl cyanide compound in the copolymer (BI)) relative to the total mass of the monomer mixture is 10 to 30 mass %, and the mass average molecular weight of the copolymer (BI) is 50,000 to 150,000 as calculated using standard polystyrene standards by GPC.

[0037] The content of repeating units derived from a vinyl cyanide compound in all repeating units constituting the copolymer (BI) is preferably 12 to 28 mass%, more preferably 15 to 26 mass%, and even more preferably 20 to 25 mass%. By being in this range, the thermoplastic resin composition according to the present invention has an improved balance of fluidity, plating adhesion strength of plated products, thermal cycle properties, and thermal shock properties.

[0038] The mass average molecular weight of the copolymer (BI) is preferably 60,000 to 140,000, more preferably 70,000 to 130,000, and even more preferably 80,000 to 120,000. When the mass average molecular weight of the copolymer (BI) is within this range, the fluidity of the thermoplastic resin composition according to the present invention and the balance of performances of the plating adhesion strength, thermal cycle properties, thermal shock properties, and impact strength of the plated product are improved.

[0039] Copolymer (BII) is a copolymer obtained by polymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, in which the content of the vinyl cyanide compound (i.e., the repeating units derived from the vinyl cyanide compound in copolymer (BII)) relative to the total mass of the monomer mixture is 10 to 30 mass%, and the mass average molecular weight of copolymer (BII) is greater than 150,000 and less than 300,000, as calculated using standard polystyrene standards by GPC.

[0040] The content of the vinyl cyanide compound in all repeating units constituting copolymer (BII) is preferably 20 to 30 mass%, more preferably 24 to 29.5 mass%, and even more preferably 26 to 29 mass%, which improves the fluidity of the thermoplastic resin composition according to the present invention and the balance of properties such as plating adhesion strength, thermal cycle properties, thermal shock properties, and impact strength of plated products.

[0041] The mass average molecular weight of copolymer (BII) is preferably 155,000 to 290,000, more preferably 160,000 to 270,000, and even more preferably 165,000 to 250,000. When the mass average molecular weight of copolymer (BII) is within this range, the fluidity of the thermoplastic resin composition according to the present invention and the balance of performances of the plating adhesion strength, thermal cycle properties, thermal shock properties, and impact strength of the plated product are improved.

[0042] When copolymer (BI) and copolymer (BII) are mixed to form copolymer (B) to be melt-kneaded as a material for the thermoplastic resin composition of the present invention, the mixing ratio of copolymer (BI) / copolymer (BII) is preferably 95-40% by mass / 5-60% by mass, more preferably 90-50% by mass / 10-50% by mass, and even more preferably 80-70% by mass / 20-30% by mass, where the total of copolymer (BI) and copolymer (BII) is 100% by mass. When the blend ratio of copolymer (BI) to copolymer (BII) is within this range, the thermal shock properties are further improved.

[0043] Various copolymers (B) (for example, copolymer (BI)) can be produced by copolymerizing an aromatic vinyl compound, a vinyl cyanide compound, and, if necessary, other copolymerizable compounds. As the polymerization method, any of known polymerization methods such as emulsion polymerization, suspension polymerization, bulk polymerization, or a combination thereof can be used.

[0044] When copolymer (BI), copolymer (BII), and copolymer (BV) other than copolymer (BI) and copolymer (BII) are mixed as copolymer (B) to be melt-kneaded as a material for the thermoplastic resin composition of the present invention, the mixing ratio of copolymer (BV) to the total mass of copolymer (B) is preferably 0 to 15 masses.

[0045] When the molecular weight of the whole polymer of copolymer (B) melt-kneaded as a material for the thermoplastic resin composition of the present invention is measured by a GPC method in terms of standard polystyrene, the mass average molecular weight is preferably 50,000 to 300,000, more preferably 60,000 to 280,000, even more preferably 80,000 to 250,000, and most preferably 90,000 to 200,000. In another aspect, the mass average molecular weight may be 85,000 to 200,000, 100,000 to 150,000, or 110,000 to 150,000. When the mass average molecular weight of all polymers in copolymer (B) is within this range, the performance balance of plating adhesion strength, thermal cycle properties, and thermal shock properties of plated products made from the thermoplastic resin composition of the present invention is improved.

[0046] <Other ingredients> The other components include various additives and other resins. Examples of additives include known antioxidants, light stabilizers, ultraviolet absorbers, lubricants, plasticizers, stabilizers, transesterification reaction inhibitors, hydrolysis inhibitors, release agents, antistatic agents, colorants (e.g., pigments, dyes, etc.), fillers such as carbon fiber, glass fiber, wollastonite, calcium carbonate, silica, or talc, flame retardants such as bromine-based flame retardants and phosphorus-based flame retardants, flame retardant assistants such as antimony trioxide, drip prevention agents such as fluororesins, antibacterial agents, antifungal agents, silicone oils, and coupling agents. Any of these additives may be used alone, or two or more may be used in combination. Other resins include rubber-reinforced styrene resins such as HIPS resin, ABS resin, ASA resin, AES resin, and SAS resin, AS resin, polystyrene resin, nylon resin, methacrylic resin, polyvinyl chloride resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene ether resin, and polycarbonate resin, etc. Blends of two or more of these resins may also be used, or these resins may be modified with a compatibilizer, functional group, etc.

[0047] Any of the essential components and optional components used in the present invention may be products recovered from processes such as polymerization processes, processing processes, and molding processes, or recycled products recovered from the market, provided that there is no problem with quality.

[0048] ≪Thermoplastic resin composition≫ The thermoplastic resin composition of the present invention is a melt-kneaded mixture of the rubber-containing graft copolymer (A) and the copolymer (B). The rubber-containing graft copolymer (A) is a copolymer of a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the presence of a rubbery polymer. Copolymer (B) is obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the absence of a rubber-like polymer, independently of rubber-containing graft copolymer (A).

[0049] The thermoplastic resin composition of the present invention may further contain other components in addition to the rubber-containing graft copolymer (A) and copolymer (B), as needed, within the range that does not impair the effects of the present invention. The content of the other components is preferably 0 to 25 parts by mass, more preferably 0 to 10 parts by mass, relative to 100 parts by mass of the total mass of the rubber-containing graft copolymer (A) and copolymer (B).

[0050] In order for the thermoplastic resin composition of the present invention to fully exhibit the above-mentioned effects, the total content of the rubber-containing graft copolymer (A) and the copolymer (B) relative to the total mass of the thermoplastic resin composition is preferably 75 to 100 mass%, more preferably 85 to 100 mass%, and even more preferably 95 to 100 mass%.

[0051] In the thermoplastic resin composition of the present invention, when the total mass of the rubber-containing graft copolymer (A) and the copolymer (B) is taken as 100 parts by mass, it is preferable that the content of the rubber-containing graft copolymer (A) is 20 to 60 parts by mass and the content of the copolymer (B) is 40 to 80 parts by mass, that the content of the rubber-containing graft copolymer (A) is 25 to 55 parts by mass and the content of the copolymer (B) is 45 to 75 parts by mass, and it is more preferable that the content of the rubber-containing graft copolymer (A) is 30 to 50 parts by mass and the content of the copolymer (B) is 50 to 70 parts by mass. When the contents of the rubber-containing graft copolymer (A) and copolymer (B) are each within this range, the adhesive strength characteristics, thermal cycle characteristics, thermal shock characteristics, impact resistance, or flowability in the plating process are excellent.

[0052] The calcium content of the thermoplastic resin composition of the present invention relative to the total mass is 0.30% by mass or less, more preferably 0.20% by mass or less, even more preferably 0.10% by mass or less, most preferably 0.05% by mass or less, and may be 0% by mass, which is below the detection limit. By being in this range, the plating appearance is excellent, and further, the thermal cycle characteristics and thermal shock characteristics are also excellent.

[0053] In the thermoplastic resin composition of the present invention, when the total mass of the rubber-containing graft copolymer (A) and the copolymer (B) is taken as 100 parts by mass, the content of the rubber polymer is preferably in the range of 10 to 30 parts by mass, more preferably 12 to 28 parts by mass, even more preferably 15 to 25 parts by mass, and most preferably 16 to 20 parts by mass. Within this range, the impact resistance, fluidity, adhesion strength characteristics in the plating process, thermal cycle characteristics, and thermal shock characteristics are more excellent.

[0054] The rubber-containing graft copolymer (A) used as a material for the thermoplastic resin composition of the present invention may contain a component (non-graft component) that is not grafted to the rubbery polymer. This non-graft component is not considered to be copolymer (B) because it is not polymerized as an independent copolymer (B) in the absence of the rubbery polymer. However, when the thermoplastic resin composition of the present invention is dissolved in a solvent such as THF and the soluble fraction is used as sample Z for molecular weight measurement by GPC, it may be difficult to distinguish between copolymer (B) and the non-graft component contained in this sample Z. Therefore, it is preferable for convenience to measure all of the polymers contained in sample Z without distinguishing between copolymer (B) and the non-grafted components, and to calculate the molecular weight in terms of polystyrene by the GPC method. When the molecular weights of all polymers contained in sample Z are measured in terms of standard polystyrene by the GPC method, the content of polymers having a molecular weight of less than 50,000 is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, and most preferably 4.5% by mass or less, relative to the total mass of all polymers. By setting the content within this range, the thermoplastic resin composition of the present invention will have better impact resistance and thermal shock properties.

[0055] <Method of producing thermoplastic resin composition> The thermoplastic resin composition of the present invention is produced by mixing and melt-kneading the rubber-containing graft copolymer (A), the copolymer (B), and other components used as needed. There are no particular limitations on the method for mixing and kneading the components of the thermoplastic resin composition, and any common mixing and kneading method can be used, such as kneading the mixture in an extruder, a Banbury mixer, or a kneading roll, followed by cutting and pelletizing with a pelletizer, etc. The thermoplastic resin composition of the present invention is molded into a resin molded article.

[0056] The thermoplastic resin composition of the present invention contains a rubber-containing graft copolymer (A) and a copolymer (B), and when the total mass of the rubber-containing graft copolymer (A) and the copolymer (B) is taken as 100 parts by mass, the content of the rubber-containing graft copolymer (A) is 20 to 60 parts by mass and the content of the copolymer (B) is 40 to 80 parts by mass. This allows the composition to exhibit excellent plating adhesion strength, and in thermal cycle characteristics and thermal shock characteristics, the plating appearance is less likely to change, and resin molded products with excellent impact resistance can be obtained. Furthermore, the composition also has excellent fluidity during molding processing.

[0057] ≪Resin molded products≫ The resin molded article of the present invention is made from the above-mentioned thermoplastic resin composition of the present invention. The resin molded article of the present invention can be obtained by molding the thermoplastic resin composition of the present invention. The molding method is not particularly limited. Examples of the molding method include injection molding, extrusion molding, compression molding, insert molding, vacuum molding, and blow molding.

[0058] <Plated products> The plated product of the present invention comprises the resin molded product of the present invention described above and a plating film formed on at least a part of the surface of the resin molded product. The plated product of the present invention can be obtained by subjecting the resin molded product of the present invention to a plating treatment. The plating method is not limited in any way, and examples of the plating method include electroless plating, direct plating, and non-chromium plating.

[0059] Since the plated product of the present invention uses the resin molded product of the present invention, the adhesive strength between the resin molded product and the plating film is excellent, the plating appearance is less likely to change during thermal cycle and thermal shock, and the impact resistance is also excellent.

[0060] The plated product of the present invention can be suitably used in a wide variety of applications, including OA (office automation) equipment, information and communication equipment, electronic and electrical equipment, home appliances, automobiles, and architecture. [Example]

[0061] The present invention will be explained in more detail below by way of synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples in any way as long as the gist of the present invention is not exceeded. In the following description, "parts" means "parts by mass" and "%" means % by mass.

[0062] [Measurement and evaluation method] <Volume average particle size of rubber polymer> The volume average particle diameter of the rubber polymer was measured for a water-diluted solution of the rubber polymer latex used in the synthesis of the rubber-containing graft copolymer (A) using a nanoparticle particle size distribution analyzer (Nikkiso Co., Ltd., "Nanotrac UPA-EX150") based on the principle of dynamic scattering theory.

[0063] <Composition ratio of copolymer (B)> The composition ratio of copolymer (B) (ratio of repeating units derived from the monomer) was determined by quantifying the amount of remaining monomer after the reaction using a gas chromatograph (Shimadzu Corporation, "GC-2014"), and then calculating backward from this value to determine the fixed amount (amount incorporated into the copolymer as a monomer unit).

[0064] <Mass average molecular weight (Mw) and number average molecular weight (Mn) of copolymer (B)> The copolymer (B) was dissolved in tetrahydrofuran (THF) to obtain a solution, and the retention time or elution volume of the copolymer (B) was measured using a GPC apparatus (manufactured by Tosoh Corporation, "TOSOH EcoSEC HLC-8320GPC"). Based on the measurement results, the mass average molecular weight and number average molecular weight of the copolymer (B) were calculated using the standard polystyrene conversion method.

[0065] The GPC measurement conditions were as follows: [Measurement conditions] Eluent: THF, flow rate: 0.35ml / min, injection volume: 10μl [Temperature settings] Pump oven: 40°C, column oven: 40°C [Columns used] TSKgel Supermultipore HZ-M and TSKgel guard column SuperMPHZ-M were used in series connection. [Standard Product Information] Tosoh Corporation PStQuick MP-M Part No. 0021913

[0066] In addition, when calculating the mass average molecular weight of copolymer (B), the content ratio of polymers having a molecular weight of less than 50,000 among all polymers in copolymer (B) was calculated from the area ratio of polymers having a molecular weight of less than 50,000 among the total area of ​​peaks showing the elution of all polymers (elution curve for mass average molecular weight) by chart and data analysis of the GPC measurement results.

[0067] When the copolymer (B) to be blended into the thermoplastic resin composition and melt-kneaded is a mixture of multiple types of copolymers (B) that have been synthesized individually, the mixture was dissolved in THF, and the resulting solution was used as a measurement sample, and the result was measured using the above-mentioned GPC apparatus to calculate "the content ratio of polymers having a molecular weight of less than 50,000 among all polymers of all copolymers (B) blended into the thermoplastic resin composition."

[0068] When the copolymer (B) to be blended into the thermoplastic resin composition and melt-kneaded is a mixture of multiple types of copolymers (B) that have been synthesized individually, the mixture was dissolved in THF, and the resulting solution was used as a measurement sample, and the measurement was performed using the above-mentioned GPC apparatus to calculate the "mass average molecular weight of all copolymers (B) blended into the thermoplastic resin composition." <Mass Average Molecular Weight (Mw) and Number Average Molecular Weight (Mn) of Acetone-Soluble Fraction of Rubber-Containing Graft Polymer (A)> In the method for measuring the mass average molecular weight (Mw) and number average molecular weight (Mn) of the copolymer (B), the mass average molecular weight (Mw) and number average molecular weight (Mn) of the acetone soluble portion of the rubber-containing graft polymer (A) were measured by replacing "copolymer (B)" with "acetone soluble portion of the rubber-containing graft polymer (A)."

[0069] [Synthesis example of rubber-containing graft copolymer (A)] <Synthesis Example 1: Production of Rubber-Containing Graft Copolymer (A-1)> A nitrogen-purged reactor was charged with 125 parts of purified water, 0.5 parts of glucose, 0.5 parts of sodium pyrophosphate, 0.005 parts of ferrous sulfate, 32 parts (solids equivalent) of a polybutadiene (BR) latex with a volume average particle size of 300 nm, and 8 parts (solids equivalent) of a polybutadiene (BR) latex with a volume average particle size of 600 nm (volume average particle size of the mixed BR: 360 nm). The temperature inside the reactor was raised to 65°C with stirring. Polymerization was initiated when the internal temperature reached 65°C. 43.2 parts of styrene (ST), 16.8 parts of acrylonitrile (AN), and 0.2 parts of a chain transfer agent t-dodecyl mercaptan mixture were continuously added over 5 hours. Simultaneously, an aqueous solution of cumene hydroperoxide (0.2 parts) and disproportionated rosin acid sodium salt (0.4 parts), which served as a polymerization initiator, was continuously added over 7 hours to complete the reaction. To the obtained latex, 1 part of 2,2'-methylenebis(4-methyl-6-t-butylphenol) was added per 100 parts of the solid content of the latex. Subsequently, the latex (100 parts of the polymer component) was coagulated using 5% sulfuric acid in a ratio of 2 parts of coagulant, followed by washing, filtration, and drying to obtain a powdery rubber-containing graft copolymer (A-1). The rubber-containing graft copolymer (A-1) had a rubber content of 40.1% and a graft ratio of 62%. The acetone solubles contained 27.2% vinyl cyanide monomer, a mass average molecular weight (Mw) of 122,000, and a molecular weight distribution (Mw / Mn) of 2.9.

[0070] <Synthesis Example 2: Production of Rubber-Containing Graft Copolymer (A-2)> A nitrogen-purged reactor was charged with 125 parts of purified water, 0.5 parts of glucose, 0.5 parts of sodium pyrophosphate, 0.005 parts of ferrous sulfate, and 50 parts of polybutadiene (BR) latex with a volume average particle size of 300 nm (solids content equivalent). The temperature inside the reactor was raised to 65°C with stirring. Polymerization began when the internal temperature reached 65°C. 36 parts of styrene (ST), 14 parts of acrylonitrile (AN), and a mixture of this and chain transfer agents (0.12 parts of terpinolene, 0.13 parts of α-methylstyrene dimer) were continuously added over 5 hours. Simultaneously, an aqueous solution of polymerization initiators (0.2 parts of cumene hydroperoxide and 0.4 parts of disproportionated rosin acid sodium salt) was continuously added over 7 hours to complete the reaction. To the obtained latex, 1 part of 2,2'-methylenebis(4-methyl-6-t-butylphenol) was added per 100 parts of the solid content of the latex, and then the latex (100 parts of the polymer component) was coagulated using 5% sulfuric acid so that the ratio of the coagulant was 2 parts, followed by washing, filtration, and drying to obtain a powdery rubber-containing graft copolymer (A-2). The rubber-containing graft copolymer (A-2) had a rubber content of 49.8% and a graft ratio of 60%. The acetone solubles contained 27.2% vinyl cyanide monomer, a mass average molecular weight (Mw) of 280,000, and a molecular weight distribution (Mw / Mn) of 4.9.

[0071] <Synthesis Example 3: Production of Rubber-Containing Graft Copolymer (A-3)> A nitrogen-purged reactor was charged with 125 parts of purified water, 0.5 parts of glucose, 0.5 parts of sodium pyrophosphate, 0.005 parts of ferrous sulfate, and 40 parts of polybutadiene (BR) latex with a volume average particle size of 200 nm (solids content equivalent). The temperature inside the reactor was raised to 65°C with stirring. Polymerization began when the internal temperature reached 65°C. 44.4 parts of styrene (ST), 15.6 parts of acrylonitrile (AN), and 0.22 parts of a chain transfer agent t-dodecyl mercaptan mixture were continuously added over 5 hours. Simultaneously, an aqueous solution of cumene hydroperoxide (0.2 parts) and disproportionated rosin acid sodium salt (0.4 parts), which served as a polymerization initiator, was continuously added over 7 hours to complete the reaction. To the obtained latex, 1 part of 2,2'-methylenebis(4-methyl-6-t-butylphenol) was added per 100 parts of the solid content of the latex, and then the latex (100 parts of the polymer component) was coagulated using 5% sulfuric acid so that the ratio of the coagulant was 2 parts, followed by washing, filtration, and drying to obtain a powdery rubber-containing graft copolymer (A-3). The rubber-containing graft copolymer (A-3) had a rubber content of 40.2% and a graft ratio of 80%. The acetone solubles contained 27.2% vinyl cyanide monomer, a mass average molecular weight (Mw) of 90,000, and a molecular weight distribution (Mw / Mn) of 2.5.

[0072] <Synthesis Example 4: Production of Rubber-Containing Graft Copolymer (A-4)> A nitrogen-purged reactor was charged with 125 parts of purified water, 0.5 parts of glucose, 0.5 parts of sodium pyrophosphate, 0.005 parts of ferrous sulfate, and 65 parts of polybutadiene (BR) latex with a volume average particle size of 300 nm (solids content equivalent). The temperature inside the reactor was raised to 65°C with stirring. Polymerization began when the internal temperature reached 65°C. 24.5 parts of styrene (ST), 10.5 parts of acrylonitrile (AN), and 0.19 parts of a chain transfer agent t-dodecyl mercaptan mixture were continuously added over 5 hours. Simultaneously, an aqueous solution of cumene hydroperoxide (0.18 parts) and disproportionated rosin acid sodium salt (0.4 parts), which served as a polymerization initiator, was continuously added over 7 hours to complete the reaction. To the obtained latex, 1 part of 2,2'-methylenebis(4-methyl-6-t-butylphenol) was added per 100 parts of the solid content of the latex, and then the latex (100 parts of the polymer component) was coagulated using 5% sulfuric acid so that the ratio of the coagulant was 2 parts, followed by washing, filtration, and drying to obtain a powdery rubber-containing graft copolymer (A-4). The rubber-containing graft copolymer (A-4) had a rubber content of 64.9% and a graft ratio of 39%. The acetone solubles contained 27.2% vinyl cyanide monomer, a mass average molecular weight (Mw) of 115,000, and a molecular weight distribution (Mw / Mn) of 3.9.

[0073] [Synthesis example of copolymer (B)] <Synthesis example 5: Copolymer (BI-1)> After purging the air in a ribbon-type stainless steel autoclave with nitrogen, 76.5 parts by mass of styrene, 23.5 parts by mass of acrylonitrile, and 20 parts by mass of toluene were continuously added to the reaction vessel. A solution of 0.26 parts by mass of tert-dodecyl mercaptan and 5 parts by mass of toluene as a molecular weight modifier and a solution of 0.1 parts by mass of 1,1'-azobis(cyclohexane-1-carbonitrile) and 5 parts by mass of toluene as a polymerization initiator were continuously fed. The temperature was controlled at 110°C and polymerization was carried out. After the polymerization conversion reached 75%, the resulting copolymer solution was directly devolatilized using a twin-screw, three-stage vented extruder to remove unreacted monomer and solvent, yielding copolymer (BI-1). The resulting copolymer had a mass-average molecular weight of 95,000 and a vinyl cyanide compound content of 23.5%.

[0074] <Synthesis Example 6: Copolymer (BI-2)> Copolymer (BI-2) was obtained in the same manner as in Synthesis Example 5, except that 0.47 parts by mass of tert-dodecyl mercaptan was used as the molecular weight modifier. The mass average molecular weight of the obtained copolymer was 55,000, and the content of vinyl cyanide compound was 23.5%.

[0075] <Synthesis Example 7: Copolymer (BI-3)> Copolymer (BI-3) was obtained in the same manner as in Synthesis Example 5, except that 86.0 parts by mass of styrene, 14.0 parts by mass of acrylonitrile, and 0.50 parts by mass of tert-dodecyl mercaptan as a molecular weight modifier were used. The mass average molecular weight of the obtained copolymer was 40,000, and the content of vinyl cyanide compound was 14.0%.

[0076] <Synthesis Example 8: Copolymer (BI-4)> Copolymer (BI-4) was obtained in the same manner as in Synthesis Example 7, except that 0.36 parts by mass of tert-dodecyl mercaptan was used as the molecular weight modifier. The mass average molecular weight of the obtained copolymer was 75,000, and the content of vinyl cyanide compound was 14.0%.

[0077] <Synthesis Example 9: Copolymer (BI-5)> Copolymer (BI-6) was obtained in the same manner as in Synthesis Example 5, except that 81.0 parts by mass of styrene, 19.0 parts by mass of acrylonitrile, and 0.20 parts by mass of tert-dodecyl mercaptan as a molecular weight modifier were used. The mass average molecular weight of the obtained copolymer was 120,000, and the content of vinyl cyanide compound was 19.0%.

[0078] <Synthesis Example 10: Copolymer (BI-6)> A reactor was charged with 125 parts of water, 0.5 parts of calcium phosphate (TCP), 0.003 parts of potassium alkenyl succinate, 0.05 parts of 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 0.04 parts of 1,1-di(t-hexylperoxy)cyclohexane, 0.04 parts of t-butylperoxy-2-ethylhexyl carbonate, 0.38 parts of t-dodecyl mercaptan, and a monomer mixture consisting of 76.5 parts of styrene and 23.5 parts of acrylonitrile. The reaction was heated from an initial temperature of 65 ° C for 6.5 hours, and then allowed to reach 125 ° C. After further reaction at 125 ° C. for 1 hour, a copolymer slurry was obtained. After cooling, the slurry was centrifuged and washed with 200 parts of water to obtain copolymer (BI-6). The resulting copolymer had a mass average molecular weight of 95,000, a vinyl cyanide compound content of 23.5%, and a residual Ca content derived from TCP of 0.05%.

[0079] <Synthesis Example 11: Copolymer (BI-7)> A copolymer slurry was obtained in the same manner as in Synthesis Example 10, except that calcium phosphate (TCP) was used in an amount of 0.8 parts. After cooling, the slurry was centrifuged and washed with 100 parts of water to obtain copolymer (BI-7). The polymer composition of the obtained copolymer was the same as that of copolymer (BI-6), and the residual Ca content derived from TCP was 0.3%.

[0080] <Synthesis Example 12: Copolymer (BI-8)> A copolymer slurry was obtained in the same manner as in Synthesis Example 11. After cooling, the slurry was centrifuged and washed with 45 parts of water to obtain copolymer (BI-8). The polymer composition of the obtained copolymer was the same as that of copolymer (BI-8), and the residual Ca content derived from TCP was 0.6%.

[0081] <Synthesis Example 13: Copolymer (BII-1)> After purging the air in a ribbon-type stainless steel autoclave with nitrogen, 72.5 parts by mass of styrene, 27.5 parts by mass of acrylonitrile, and 20 parts by mass of toluene were continuously added to the reaction vessel. A solution of 0.19 parts by mass of tert-dodecyl mercaptan and 5 parts by mass of toluene as a molecular weight modifier and a solution of 0.1 parts by mass of 1,1'-azobis(cyclohexane-1-carbonitrile) and 5 parts by mass of toluene as a polymerization initiator were continuously fed. The temperature was controlled at 110°C and polymerization was carried out. After the polymerization conversion reached 75%, the resulting copolymer solution was directly devolatilized using a twin-screw, three-stage vented extruder to remove unreacted monomers and solvent, yielding copolymer (BII-1). The resulting copolymer had a mass-average molecular weight of 185,000 and a vinyl cyanide compound content of 27.5%.

[0082] <Synthesis Example 14: Copolymer (BII-2)> Copolymer (BII-2) was obtained in the same manner as in Synthesis Example 13, except that 81.0 parts by mass of styrene, 19.0 parts by mass of acrylonitrile, and 0.20 parts by mass of tert-dodecyl mercaptan as a molecular weight modifier were used. The mass average molecular weight of the obtained copolymer was 175,000, and the content of vinyl cyanide compound was 19.0%.

[0083] <Synthesis Example 15: Copolymer (BII-3)> Copolymer (BII-3) was obtained in the same manner as in Synthesis Example 13, except that 65.0 parts by mass of styrene, 35.0 parts by mass of acrylonitrile, and 0.18 parts by mass of tert-dodecyl mercaptan as a molecular weight modifier were used. The mass average molecular weight of the obtained copolymer was 185,000, and the content of vinyl cyanide compound was 35.0%.

[0084] <Synthesis Example 16: Copolymer (BII-4)> A reactor was charged with 125 parts of water, 0.5 parts of calcium phosphate (TCP), 0.003 parts of potassium alkenyl succinate, 0.05 parts of 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 0.04 parts of 1,1-di(t-hexylperoxy)cyclohexane, 0.04 parts of t-butylperoxy-2-ethylhexyl carbonate, 0.18 parts of t-dodecyl mercaptan, and a monomer mixture consisting of 73.5 parts of styrene and 27.5 parts of acrylonitrile. The reaction was heated from an initial temperature of 65 ° C for 6.5 hours, and then allowed to reach 125 ° C. After further reaction at 125 ° C. for 1 hour, a copolymer slurry was obtained. After cooling, the slurry was centrifuged and washed with 200 parts of water to obtain copolymer (BII-4). The resulting copolymer had a mass average molecular weight of 185,000, a vinyl cyanide compound content of 27.5%, and a residual Ca content derived from TCP of 0.05%.

[0085] <Examples 1 to 13 and Comparative Examples 1 to 4> (Production of Thermoplastic Resin Composition) The rubber-containing graft copolymer (A), copolymers (BI) and (BII), and 0.5 parts of Kao Wax EB-G (trade name) (ethylene bisstearamide) manufactured by Kao Corporation were mixed in the proportions shown in Table 1, and the mixture was melt-kneaded to prepare a thermoplastic resin composition. The mixture of materials was melt-kneaded at a temperature of 200°C using a 30 mm twin-screw extruder ("TEX30α" manufactured by The Japan Steel Works, Ltd.) and pelletized to obtain pellets of a thermoplastic resin composition. The thermoplastic resin compositions of the examples were evaluated as follows, and the results are shown in Table 1.

[0086] <Calcium (Ca) content> The thermoplastic resin composition was burned in an electric furnace to turn it into ashed material, and the Ca content was calculated using a fluorescent X-ray analyzer (HITACHI Hi-Tech Science, model: EA6000VX).

[0087] <Proportion of polymers with molecular weights of less than 50,000 contained in thermoplastic resin composition> A solution of the soluble matter obtained by dissolving the thermoplastic resin composition in tetrahydrofuran (THF) was used as a measurement sample, and the retention time or elution volume of the eluted polymer was measured using a GPC apparatus (manufactured by Tosoh Corporation, "TOSOH EcoSEC HLC-8320GPC") under the same measurement conditions as for copolymer (B). Based on the measurement results, the molecular weight of the eluted polymer was calculated using the standard polystyrene conversion method. The content of polymers having a molecular weight of less than 50,000 among all the eluted polymers was calculated by data analysis (slice data) of the GPC measurement results, as the proportion corresponding to the area occupied by polymers having a molecular weight of less than 50,000 among the total area of ​​the peaks showing the elution of the polymers (elution curve for mass average molecular weight).

[0088] <Ratio of Copolymer (B) Having a Mass Average Molecular Weight of 50,000 to 300,000 Among Multiple Copolymers (B) Polymerized Individually and Blended into Thermoplastic Resin Composition> As shown in Table 1, either (BI) or (BII) polymerized individually was combined and blended into a thermoplastic resin composition. The content ratio of copolymers (B) having a mass average molecular weight of 50,000 to 300,000 relative to the total mass of all blended copolymers (B) was calculated.

[0089] <Proportion of polymers containing 10 to 30 mass% of repeating units derived from vinyl cyanide compound in all copolymers (B) blended in thermoplastic resin composition> For each of (BI) and (BII) blended as copolymer (B), the ratio was calculated from the monomer composition blended during polymerization. In all examples, all blended copolymers (B) were polymers in which the repeating unit derived from a vinyl cyanide compound accounted for 10 to 30% by mass relative to 100% by mass of all repeating units. In other words, the proportion of the above polymer was 100% by mass in all examples.

[0090] (Evaluation of plating adhesion strength) The thermoplastic resin composition pellets were injection molded using an 80-ton injection molding machine (J80ADS-110U, manufactured by The Japan Steel Works, Ltd.) to obtain test pieces. Injection molding was carried out using a mold for evaluating plating adhesion strength (90 mm long x 50 mm wide x 3 mm thick) at a cylinder temperature of 250°C, a mold temperature of 60°C, and a medium injection speed (15 mm / sec). The obtained test pieces were plated, and the plating film was peeled off in the vertical direction on a load measuring device to measure the strength, and the plating adhesion strength was judged according to the following criteria. ◎: The plating adhesion strength is 12N / cm or more, which is very excellent. Good: The plating adhesion strength is 10 N / cm or more and less than 12 N / cm, and there is no problem in practical use. △: Plating adhesion strength is 8N / cm or more and less than 10N / cm, and it can be used if the application is limited. ×: Plating adhesion strength is less than 8N / cm and unusable.

[0091] In the evaluation of plating adhesion strength, plating processing was carried out according to the following steps (1) to (15). (1) Degreasing process [5 minutes at 50°C] ⇒ (2) Water rinsing ⇒ (3) Etching treatment {CrO3: 400 g / l, sulfuric acid: 200 cc / l} [15 minutes at 65°C] ⇒ (4) Water rinsing ⇒ (5) Acid treatment [1 minute at 23°C] ⇒ (6) Water rinsing ⇒ (7) Catalysis treatment [3 minutes at 30°C] ⇒ (8) Water rinsing ⇒ (9) Activation treatment [3 minutes at 40°C] ⇒ (10) Water rinsing ⇒ (11) Chemical Ni plating [5 minutes at 40°C] ⇒ (12) Water rinsing ⇒ (13) Electrolytic copper plating [film thickness: 35 μm, 60 minutes at 20°C] ⇒ (14) Water rinsing ⇒ (15) Drying [2 hours at 80°C]

[0092] (Evaluation of thermal cycle characteristics) The thermoplastic resin composition pellets were injection molded to obtain test pieces using an 80-ton injection molding machine ("J80ADS-110U" manufactured by The Japan Steel Works, Ltd.) The injection molding was carried out using a thermal cycle evaluation mold (100 mm long x 100 mm wide x 3 mm thick) under the following conditions: cylinder temperature 230°C, mold temperature 60°C, and injection speed 50 mm / sec. The resulting test pieces were plated and subjected to a thermal cycle test using a Hitachi Global Life Solutions, Inc., Model EC-86MTPE, thermal cycle tester. The temperature was lowered from 23°C to -30°C over 30 minutes, held at -30°C for 1 hour, then raised to 23°C over 30 minutes and held at 23°C for 15 minutes. The temperature was then raised to 80°C over 30 minutes and held at 80°C for 1 hour. The temperature was then lowered to 23°C over 30 minutes and held at 23°C for 15 minutes. This cycle constituted one cycle, and 20 cycles were performed. The condition of the plating film on the product was then visually observed, and the thermal cycle characteristics were evaluated according to the following criteria. ◎: No change in plating film, very good. ◯: There is some swelling in the plating film, but this does not pose a problem in practical use. △: There are changes such as swelling in the plating film, but it can be used if the application is limited. ×: The plating film has undergone significant changes such as swelling, and is not of a practical level.

[0093] In the evaluation of thermal cycle characteristics, plating was carried out according to the following steps (1) to (17). (1) Degreasing process [5 minutes at 50°C] ⇒ (2) Water rinsing ⇒ (3) Etching treatment {CrO3: 400 g / l, sulfuric acid: 200 cc / l} [20 minutes at 65°C] ⇒ (4) Water rinsing ⇒ (5) Acid treatment [1 minute at 23°C] ⇒ (6) Water rinsing ⇒ (7) Catalysis treatment [3 minutes at 30°C] ⇒ (8) Water rinsing ⇒ (9) Activation treatment [3 minutes at 40°C] ⇒ (10) Water rinsing ⇒ (11) Chemical Ni plating [5 minutes at 40°C] ⇒ (12) Water rinsing ⇒ (13) Copper electroplating [film thickness: 20 μm, 20 minutes at 20°C] ⇒ (14) Water rinsing ⇒ (15) Ni electroplating [film thickness: 10 μm, 15 minutes at 55°C] ⇒ (16) Water rinsing ⇒ (17) Cr electroplating [film thickness: 0.3 μm, 2 minutes at 45°C]

[0094] (Evaluation of thermal shock characteristics) Using the same plated products as in the evaluation of thermal cycle properties, a Hitachi Global Life Solutions, Inc., Model ES-306L thermal shock tester was used. The products were held in a tank cooled to -30°C for one hour, then heated to 80°C within 10 minutes, held at 80°C for one hour, cooled to -30°C within 10 minutes, held at -30°C for one hour, then heated again to 80°C and held at 80°C for one hour. This cycle was repeated, and after the 20th cycle, the products were held at 80°C for one hour, allowed to cool, and the samples were removed and the condition of the plating film on the products was visually observed to determine the thermal shock properties. ◎: No change in plating film, very good. ◯: There is some swelling in the plating film, but this does not pose a problem in practical use. △: There are changes such as swelling in the plating film, but it can be used if the application is limited. ×: The plating film has undergone significant changes such as swelling, and is not of a practical level.

[0095] (Charpy impact strength evaluation) The thermoplastic resin composition pellets were injection molded using a 100-ton injection molding machine (FANUC ROBOSHOT α-S100iB, manufactured by FANUC Corporation) to obtain test pieces (length 80 mm, width 10 mm, thickness 4 mm). The injection molding was performed at a molding temperature of 235°C and a mold temperature of 60°C. The Charpy impact strength (notched) of the obtained test piece was measured in accordance with ISO 179 at a measurement temperature of 23°C, and the impact resistance was judged according to the following criteria. ◎: Charpy impact strength is 20kJ / m 2 That's all and it's very excellent. ○: Charpy impact strength is 15kJ / m 2 More than 20kJ / m 2 This is less than the limit, and there is no practical problem. △: Charpy impact strength is 15kJ / m 2 This is less than the practical level.

[0096] (Evaluation of fluidity (spiral flow)) Using a spiral flow mold (width 15 mm × thickness 2 mm), pellets of the thermoplastic resin composition were injection molded from an 85-ton injection molding machine ("J85AD-110H" manufactured by The Japan Steel Works, Ltd.) under conditions of a cylinder temperature of 270°C, a mold temperature of 60°C, and an injection pressure of 100 MPa. The spiral flow length (mm) of the obtained molded product was measured, and the fluidity (spiral flow) was evaluated according to the following criteria. ◎: The spiral flow length is 470 mm or more, and the material is excellent. Good: The spiral flow length is 450 mm or more and less than 470 mm, and there is no problem in practical use. △: The spiral flow length is between 430 mm and 450 mm, and it can be used if the application is limited. ×: The spiral flow length is less than 430 mm, which is not practical.

[0097] (Molded appearance) The entire surface of the test piece (length 90 mm x width 50 mm x thickness 3 mm) formed for measuring plating adhesion strength before plating processing was visually observed. ○: 0 to 2 lumps, excellent appearance. △: There are 3 to 4 lumps and the appearance is inferior to that of "◯". ×: There are 5 or more lumps, and the appearance is extremely poor compared to "◯".

[0098] (plating appearance) The entire surface of the test piece (length 90 mm x width 50 mm x thickness 3 mm) formed after plating to measure the plating adhesion strength was visually observed. ○: 0 to 2 lumps, excellent appearance. △: There are 3 to 4 lumps and the appearance is inferior to that of "◯". ×: There are 5 or more lumps, and the appearance is extremely poor compared to "◯".

[0099] [Table 1A]

[0100] [Table 1B]

[0101] [Table 1C]

[0102] [Table 1D]

[0103] It is clear that the thermoplastic resin compositions of Examples 1 to 13 give resin molded articles excellent in plating adhesion strength properties, thermal cycle properties, thermal shock properties, impact resistance, fluidity, molding appearance, and plating appearance. The plating appearance of Example 11 was inferior to that of the other Examples, which is thought to be due to the slightly high Ca content in the thermoplastic resin composition. The thermal shock properties of Example 12 were inferior to those of the other Examples, which is believed to be because copolymer (B) does not contain (BII). The plating adhesion strength and thermal cycle properties of Example 13 were inferior to those of the other Examples, which is thought to be due to the fact that the mass average molecular weight of the copolymer (B) was somewhat low and that (BII) was not contained.

[0104] The thermoplastic resin composition of Comparative Example 1 had a high Ca content and was therefore inferior in thermal cycle properties, thermal shock properties, molded appearance, and plating appearance. The thermoplastic resin compositions of Comparative Examples 2 to 4 had a high content of polymers with molecular weights of less than 50,000 in the total copolymer (B) blended therein, and therefore had poor impact resistance and plating adhesion strength, as well as poor thermal cycle properties and thermal shock properties. [Industrial Applicability]

[0105] According to the present invention, it is possible to provide a thermoplastic resin composition capable of producing a resin molded article having excellent adhesion strength, thermal cycle properties, thermal shock properties, impact resistance, fluidity, and appearance in a plating process, and a resin molded article and a plated article obtained by molding the thermoplastic resin composition. Therefore, the present invention is extremely important from an industrial viewpoint.

Claims

1. a rubber-containing graft copolymer (A) obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound in the presence of a rubber polymer; a thermoplastic resin composition which is a melt-kneaded mixture of the rubber-containing graft copolymer (A) and a copolymer (B) which is independent of the rubber-containing graft copolymer (A) and is obtained by copolymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, the rubber-containing graft copolymer (A) is mixed with 20 to 60 parts by mass of the copolymer (B) and the copolymer (A) is mixed with 40 to 80 parts by mass of the copolymer (B) relative to 100 parts by mass in total of the rubber-containing graft copolymer (A) and the copolymer (B); when the molecular weights of all polymers in the copolymer (B) are measured by a GPC method in terms of standard polystyrene, the proportion of polymers having a molecular weight of less than 50,000 is 20 mass% or less based on the total mass of all polymers, the total content of the rubber-containing graft copolymer (A) and the copolymer (B) relative to the total mass of the thermoplastic resin composition is 75 to 100 mass%, A thermoplastic resin composition, wherein the calcium content in the thermoplastic resin composition is 0.30 mass% or less relative to the total mass of the thermoplastic resin composition.

2. 2. The thermoplastic resin composition according to claim 1, wherein, among all polymers of the copolymer (B), a proportion of polymers in which a proportion of repeating units derived from a vinyl cyanide compound is 10 to 30 mass% of all repeating units is 85 to 100 mass% with respect to the total mass of all polymers.

3. the copolymer (B) is a mixture of a plurality of copolymers (B), 3. The thermoplastic resin composition according to claim 2, wherein, when the mass average molecular weight of each copolymer (B) is measured in terms of standard polystyrene by a GPC method, the mixing ratio of copolymer (B) having a mass average molecular weight of 50,000 to 300,000 relative to the total mass of the mixture is 85 to 100 mass%.

4. the copolymer (B) is a mixture of copolymer (BI) and copolymer (BII), the copolymer (BI) is a copolymer obtained by polymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, the content of the vinyl cyanide compound relative to the total mass of the monomer mixture is 10 to 30 mass%, and the mass average molecular weight of the copolymer (BI) is 50,000 to 150,000 in terms of standard polystyrene measured by a GPC method, The thermoplastic resin composition according to claim 1, wherein the copolymer (BII) is a copolymer obtained by polymerizing a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound, the content of the vinyl cyanide compound relative to the total mass of the monomer mixture is 10 to 30 mass%, and the mass average molecular weight of the copolymer (BII) calculated as standard polystyrene by a GPC method is more than 150,000 to 300,000.

5. 2. The thermoplastic resin composition according to claim 1, wherein the calcium content in the thermoplastic resin composition is 0.20 mass% or less relative to the total mass of the thermoplastic resin composition.

6. A resin molded article made of the thermoplastic resin composition according to any one of claims 1 to 5.

7. A plated product having a plating film on at least a portion of the surface of the resin molded product according to claim 6.